1. Field of the Invention
This invention relates to latch control for explosion relief panels and more particularly to a magnetically controlled latch.
2. Description of the Prior Art
It has heretofore been proposed to utilize closures or panels which are releasable by pressure applied thereon due to an explosion or which is in excess of a predetermined pressure level.
Schibli et al., in U.S. Pat. No. 3,861,080 show springs for retention of the closure while Hawes et al., in U.S. Pat. No. 3,332,175 show a vacuum chamber for panel retention.
Abeel, in U.S. Pat. No. 3,571,977 shows spring retained door latch mechanism released upon attainment of a predetermined internal pressure.
Bernhard, in U.S. Pat. No. 2,514,927, shows in FIGS. 1 to 4 a magnetic door holder in which the keeper 19 can be manually released from pole pieces 16 and 17 which are energized through pole plates 11 and 12 from a block 10 of magnetized material. The release is effected by handles 30, 31 on a pivotally mounted lever 20 on which the keeper 19 is carried so that less force is required than the holding force of the magnet. In FIGS. 5 and 6 a foot pedal 46 is provided for slidably separating the keeper plate 41 from the magnet 40. These structures with their manual or foot pedal release are wholly unsuited for the accurately controlled automatic pressure release of explosion doors or the like.
Reilly, in U.S. Pat. No. 3,453,777, shows a pressure venting panel assembly in which a pivotally mounted panel is secured by a magnetic latch. The magnet 76 is mounted to a bracket 72 on the window frame 12 for engagement either by a keeper 20, of magnetically attractive material such as iron, nickel or a magnetic alloy mounted on the casement 28, or by the casement 28 itself, if of magnetically attractive material. The magnetic latch and its mounting and with its use of a pivotally mounted panel and with no sealing of the panel have little in common with the invention hereinafter described with its linearly movable panel with spring loading and would not function in a comparable manner.
Sieverin, in U.S. Pat. No. 3,502,361 shows a magnetically biased tank vent. A flange 12 on a base 10 has an annular seat 14. A circular cover 16, hingedly mounted by hinge pin 18 to the base 10 with a diaphragm 20 engageable with the seat 14 for sealing. If the diaphragm 20 is to seal deflection of the diaphragm against a spring force must be available for that purpose. Exteriorly of the diaphragm 20 a plate 24 is provided on the cover 16 loosely carried on a bolt 26 for clearance adjustment and locked against rotation by a roll pin 32. The resilience of the diaphragm would be a force effective in opposition to the magnetic force. The Sieverin structure lacks a linearly movable panel, spring loading effective on the panel, seals which are effective normal to the forces moving the panel, and reliable and predictable release of the keeper from the magnet.
Elrod et al., in U.S. Pat. No. 3,844,597 shows a safety latch in which a permanent magnet is employed for maintaining the latch in engaging alignment.
None of the prior art devices show a rigid linearly movable light weight low inertia panel subject to pressure, held by an arm, with a pivotally mounted fork assembly having a keeper for engagement with a magnet carried by the arm, and with an adjustable length post carried by the panel for actuating the fork assembly for release and which is capable of repetitive action at relatively low pressure levels.